[R-sig-ME] subjects assigned to treatment groups, multiple repeated measures over time

[P Greenwood]

Hello

I am a new user of lme4 and cannot find a clear answer to how to handle subjects randomly assigned to condition (treatment)  groups. The subject to subject variability  is likely to differ between groups on my measures in a way that varies over time. Time is broken into to 5 “drives” which occur in order (drive 1 is first, drive 2 is second, etc). Each drive has 10 trials on which various measures are obtained - heart rate, alpha band power at Pz, eye gaze, etc..
 
Initially, I want to predict reaction time (RT) as a function of condition, alpha band power (PzAlpha), and drive.  

This model runs, but I’m not sure whether I am handling subjects within group correctly.
I plan to use Anova to compare a null model with a simpler model, once I understand how to handle subjects within groups.

Here is my model and output as a screen shot. Thanks so very much...

sumModelInteraction20 <- lmer(RT ~ 1 + Condition + PzAlpha + Drive + Condition*PzAlpha*Drive + (1 | Subject) + (1 | Trial), data = INFAST_Behavioral)


P.M. Greenwood, Ph.D.
Associate Professor of Psychology
Editorial Board, NeuroImage
David King Hall 2052
George Mason University
MSN 3F5, 4400 University Drive
Fairfax, VA 22030-4444

Ph: 703 993-4268
fax: 703 993-1359
email: Pgreenw1 at gmu.edu
http://psychology.gmu.edu/people/pgreenw1